Sound reproducing apparatus



Aug. 9, 1932.

G. F. C. BAUER SOUND REPRODUCING APPARATUS Filed Oct. l5, 1929 2Sheets-Sheet 2 Lim' Patented Aug.; 19.32

yUNITED STATES PATENT OFFICE 'eUsTAv r. c. BAUER, or rONAW-ANDA, NEWYORK, AssIoNon 'ro NATIONAL rOLIcr:

SIGNAL COMPANY, or BUFFALO, NEW YORK, A CORPORATION or NEW roux SOUNDBEPRODUCING .APPABfA'JJUS- This invention relates to a soundreproducing, apparatus and more particularly to that type of phonographin which the is reproduced through a needle traversinga hard recordwhich has been formed through the original rendition of the music orother vsounds to be reproduced lalthough the invention can also beemployed in reproducing sounds directly as\from a diaphragm or from anyotherl orm of record One of the principal objects of this invention isto provide such a device which will give a faithful and clearreproduction of the sound recorded on the record through electricalmeans, and in which inparticular, the full range of vibrations andovertones are reproduced exactly as originally produced,4

such overtones being usually lost in the mechanical reproduction ofsound.

Another aim is to provide such a reproducer in which the elementsvibrated by the needle traversing the record are light in weight so asto' be sensitive to the slighter vibrations of the needle. 25 ,A furtheraim is to provide an electrical sound reproducer in which thereproduction is eli'ected through the microphonic action of an electrontube, such as are used in radios. By rigidly holding all but one of theelements of an electron tube and `vibrating the other through a preparedrecord or thelike, the audio-frequency impulses from the tube can beamplified to give a clear and undistorted reproduction of the sound.

Another object is to provide such a sound reproducing apparatus whichemploys any well known audio circuit. By this means the invention isparticularly applicable to radio-- phonographs since the same audiocircuit can be used for both the radio and the phonograph.

Another purpose is to so mount the electron tube as to be extremelysensitive tothe vibrations of the needle and is so mounted that it canbe easily replaced, and new needles inserted as they become worn.

Other aims are to provide such an apparatus which can be produced at lowcost, is durable and in which, in particular, the three elementelectrontube will 'vereand constant use., p v

In the accompanying drawings: n

Figure 1 is a diagrammatic view of a suitable form of audio circuitshowing the manner in which a three element electron tube and anelectrical reproducer or loud speaker can be arranged to reproducesounds in accordance with my invention.

Figure 2 is aside elevation of a tone arm, partly broken away, showingthe manner in which the three element electron tube is mounted andvibrated through a record. Y

Figure 3 is a fragmentary top 'plan view of the tone arm. 4

Figures 4-9are sections taken on the correspondingly numbered lines onFigure Q.

Figure 10 is 'a front elevation vof the tone arm, showing part of athree element electron tube guard or housing broken away to expose thetube Figure il is a fragmentary enlarged view similar to Fig. 2, showingthe manner in which the needle is connected to the three elementelectron tube.

Similar reference numerals lrefer to like parts in each of the severalviews.

-In its general organization, this invention comprises an audio circuitincluding a reproducer or loud speaker and -a three element 80 electrontube which tube and reproducer are operatively connected so that theaudiofrequency impulses from the tube are transmitted to the reproducer,a structure within the tube for rigidly holding two of the tubeelements, preferably the filament and the plate, against vibration andthe grid being mounted so .as to vibrate with the tube and a needleremovably carried by the tube and adapted to traverse the track of arecord so that the 90 vibrations recorded on the record are transmittedto the vibratory grid. The vibration of the grid varies the electronflow and the audio frequency impulses from the tube, when reproduced bythe reproducen give a faithful reproduction of the sounds recorded inthe record. f

- While a three element` electron tube is preferred it will beunderstood that a two or 100 standup under sefourl element electron tubecan also be emmanner of mounting the electron tube on a tone arm of aphonograph and a specific con-` struction of a three element electrontube by which the slightervibrations and. overtones are accurately rereduced and the tube and needle are rea y replaceable as they becomeworn. l

The invention is shown as used in connection with a honograph having arevolving table 15 whic is supported on a shaft 16, this shaft servingto center a disk record 17 of hard rubber or the like and being'`revolved b an electric motor 18. The record is formed with the usualtrack for guiding a needle 19 and the track is formed so as tovibratetheneedle 19 in response to the sounds recorded. on the record.A i

The primary conception of this invention resides in the employment ofthe microphonic action of a two, three or four element electron tube toproduce audio-frequency vibrations b the vibration of one element of thetube re ative to the others. A three element electron tube 20 suitablefor this purpose is shown, the same including the usual Bakeliteposition of the f base 21 which is referably of irregular form for apurpose w ich will resently appear, and a lass bulb 22 which ouses afilament 23, 24 and plate 25. These are shown in Fig. 1 as connected toan audio circuit, the tube being connected to the audio circuit in thesame manner as a detector tube in a radio audio circuit. In the circuitshown, the grid 24 is negatively charged from the C battery through thewire 26 the plate 25 is positively charged from the B battery throughfirst audio transformer 28 and in turn is connected by wires 29 and 30with the positive terminal ofthe B battery, and the terminals of thefilament 26 are respectively connected with the negative terminal of theA battery through the wire 31 and to the positive side of the fA batterythrough the wire.32. v

In all present radio electron tube installations, the output impedanceis controlled and varied by the grid potential changes. In the presentapplication, the output impedence is varied by mechanically shifting theid in relation to the lament and the p ate without changing the relativepotential of the grid. When the grid or any other single element of achargedelectron tube is so shifted or vibrated with respect'to the otherelements, the iow of electrons from the filament to the plate iscorrespondingly affected and when the grid is mechanically vibrated ataudio-frequencies corresponding audio-frequency iuctuations occur 1n theplate current. This vibration of the elements of an electron tube andits the wire 27 which' connects with the eect upon the action of thetube is known as the microphonic action of the tube. Theseaudio-frequency fluctuations when amplified throu h the usual first andsecond audio pathetic vibration, and the third, the grid,v

1s caused to follow faithfully the vibrations of a phonograph record orthe like so that the audio-frequency fluctuations caused in theaudio-circuit will effect a reproduction of the recordedsounds in thereproducer 36.

The base 21 of the three element tube 20 is arranged in a socket -37formed at the /outer end of a tone arm 38, this tone arm be-` ingpreferabl made of Bakelite or the like and being ho ow to form a conduitreceiving the wires 26,\27 and 31 and 32 which connect with the elementsof the tube 20. This socket 37 conforms to the shape of the base 21 ofthe electron tube 20 which it receives and since the shape'of both areirregular the base can be received in one position only thereby insuringthe `proper p0- sitioning o'f the electron tube in the socket 37. Thistone arm is preferably supportedbya horizontal pivot kpin 39 between twoears 40 which permit vthe vertical movement of the tone arm andthe twoears 40 are carried by a pintle 41 which is journalled in a base 42, sothat the tone arm can follow the track of the record 17. Any form oftone arm mounting can, however, be employed.-V l

On each inner side of the socket 37 of the tone arm, a spring contact 43isv arranged in a suitable recesseach of these Acontacts being connectedwith one of the wires 26, 27, 31 and 32 and engaging one of the contacts44 at the sides of the base 21 of the three element electron tube. Thesecontacts 44 are connected to the filament, grid and plate of the tubeand the spring contacts 43 in addition to forming electrical contactsalso serve as a spring mounting for the tube which is vibrated inresponse to the recorded vibrations as hereinafter described. The

base 21 of the tube 20 is also spring supconnected to a cross member orbar 47 'made of mica or other nonconducting material.

To this mica cross bar are rigidly anchoredI the outer ends of the plate25 and the filament 23 by means of small pins 70 or the like so thatthese elements`are held against vibration. l

` The outer end of the glass bulb 22 is formed to provide a ni ple 48which receives a -stem or anchor 49. l')1`li.is stem is rigidly mountedin the nipple 48 and projects inwardly through an openin in the micacross piece 47, and to the en of. thestem 49 the outer end of the grid24 isanchored. The opening 50 is sufficiently large to permit'the stem49 to vibrate independently of the cross piece 47 and thereby insuresthe vibration of the grid in response to the vibration of the tube 20.To insure the vibration of the grid in response to very slight vibrationof the tube, the other or inner end of the 'dis referably connected toits lead ort e terminal of the wire 26 by a flexible link 51. i

On the underside of the socket 37 two ears 52 are formed which projectdownwardly and carry outwardly projecting pins 53. These pins engagebayonet slots 54 formed at the rim of a protecting casing 55 whichhouses the three element tube 20 and can be made of any suitable nonbreakable material. At its upper end an annular row of ventilationopenings 56 is provided and at its lower end or tip a relatively largeopenin is provided which is coveredby a flexible d aphragm 57. Thisdiaphragm can be made of any suitable material such as rubber and isshown as held in lace by a retaining collar 58.

needle holder 59 projects through this diaphragm 57 this needle holderhaving an upper cup shaped portion 60 which is firmly cemented orotherwise secured to thenipple 48 of the three element tube 20 and alower part which receives the needle 19, this needle being shown as heldin'place by a set screw 61. AThe needle holder is preferably supportedby the fiexible diaphragm, the diaphragm. engaging a reduced Ypartofthe.

needle holder.

With the arts arranged as described, the operation o? the apparatus inreproducing sound from the record 17 is as follows:

The record 17 is turned by the motor 18 and vibrates the needle 19following its track, this needle being' held against the record by theweight of the tone arm 38 and its associated parts. The'vibration of theneedle 19in turn vibrates its needle holder 59 and the three elementelectron tube 20 and since the needle holder is supported for vibratorymovement by the flexible diaphragm 57, and since the base of the threeelement. electron tube is spring supported in its socket by the fourcontact springs 43 and the helical spring 45, the entire tube 20 issensitive to very slight vibrations of the needle 19 and will vibrate inunison therewith.

The filament 23 and plate 25 are rigidly supported in the tube 20 btheir connection with the mica cross bar 4g of the wires 46 which extendoutwardly om the base and in construction,

"connected with the vibratory tip of the tube hence these elements ofthe tube are prevented from vibrating. The grid 24 is, however,

variation in the flow of electrons from the filament to the plate andthereby effects a` corresponding variation in the audiofrequencyimpulses of the tube, these imulses are then ampliliedby any suitableorm of audio circuit, such as shown in Fig. 1 and are reproduced assound ducer or loud speaker 36.

An electron tube having all but one of its elements held againstvibrating and the other subject to the lvibrations of the tube, whenlconnected with an audio circuit as described,v will give a clear andfaithful reproduction of the sound vibration imparted to it and willaccuratelyA and clearly reproduce the slighter vibrations and'overtonesas well as the more dominant vibration. Itis also apparent that theinvention is particularly applicable tov radio-phonographs since'thesame audio circuit can be used 1n amplifying and reproducing both forthe radio and the phonograph by the provision of suitable by areproswitching means, the three element electron l The tube of thepresent invention and its associated parts are also simple andinexpensive will stand up for a long time, and are easily replaced asmay be required. While a three element electron tube is specificallydescribed, it will be Yunderstood, that a four element or a two elementtube can also be employed, but a three element tube is preferred.

Having claim 1. A sound reproducing apparatus comprising anaudio-circuit including` a reproducer and an electron tube, having atleast fully described my invention, I

two elements, said tube and reproducer being operatively connected so'that audio-frequenc impulses from said ltube are transmitte to saidreproducer, said tube `includinga base supporting one end of said ele.

ments, a glass bulb and a supporting structure anchored in said base,-composed of a pair of supporting wires and a cross piece of insulatingmaterial connected to the ends of said supporting wire, means anchoringall but one of the elements of said tube to said cross piece and meansfor vibrating the other element of said tube.

2. A prising an audio-circuit inclu ing a repro' sound reproducing aparatus coinducer and an electron tube having at least l two elements,said tube and re roducer being operatively connected so t ataudio-frequency impulses from said tube are transmitted to saidreproducer, a means for supporting all but one of the elements of saidtube against vibration, opposite ends of the'other element of said tubeto the tip of said tube and means connected to the tip of said tube forvibrating said tube.

3.1 sound reproducing apparatus comf prising an audio-circuit includinga reproducer and an electron tube having at least two elements, saidtube and re roducer being operatively connected so t at audio-frequencyimpulses from said tubes are trans-- mitted to said reproducer, a meansfor lsu port all but one of the elements of said tu against vibration,opposite ends of the other element of said tube to opposite parts ofthebody forming said tube to vibrate therewith and means for vibrating saidtube.

4. An electron tube comprising a base, a

v bulb, at least three elements arranged in said bulb and comprising afilament, a grid and a plate each connected to said base, a pair ofsupporting wires arranged in said bulb and enclosed in said base, across piece of insulating material connecting said cross wires, meansanchoring said filament and late to said cross piece and supporting saidament and plate against vibration and means connecting said grid to saidbulb, said grid being mounted to vibrate relative to said plate and lfilament and said bulb being formed to proi quency impulses are tube tosaid reproducer, one of the elements vide means for attaching avibrating element thereto.

5. A sound reproducing apparatus comprising an audio-circuitincluding'an electron tube having at least two elements, and areproducer, said tube and reproduoer being operatively 'connected sothat audio-fretransmitted from said f of Vsaid tube being movablerelative to the other, a tone arm supporting the wires connecting saidtube and reproducer and having a socket formed at its outer end,meansfor yieldingly supporting said tube within said socket, thecontacts of said tube contacting with the contacts of said wires, aguard removably secured to said tone arm and enclosing and protectingsaid tube, said guard being provided with an opening, a record,

and a needle removably carried by said tube and projecting through saidopening, said needle being adapted to be vibrated by said record.

In testimony whereof I vailix m signature.

GUSTAV F. C. AUER.

means connecting the means connecting the,

